Multiplex telephony.



M. C. A. LATOUR.

MULTIPLEX TELEPHONY.

APPLICATION FILED MAY 27, 1905.

91 3 ,52 1 Patented Feb. 23, 1909.

3 SHEETS-SHEET l.

Inventor: marius (1A.- Latour,

. I 'i marius C.A.L,atou\, a 7- WQ;

M. G. A. LATOUR. MULTIPLEX TELEPHONY.

APPLICATION FILED MAY 27, 1905.

Patented Feb. 23, 1909.

3 SHEETS-SHEET 2.

Fig. 4.

CHMFE/VSAMR g A M16 Fig-5 I lvAll'lvlpA wL V47 V Witnesses: 6f Inventor:

M. c. A. LATOUR. MULTIPLEX TELEPEONY.

APPLICATION FILED MAY 2'], 1906.

913,521. Patented Feb.23, 1909.

3 SHEETS-SHEET 3.

VJ 1x03551351: INVENT 13 21 I Q 2. Wu EY/ $2 M, AT TY IQ MAFLIUE [1A. LATEIUH.

UNITED srnrns PATENT OFFICE.

MARIUS C. A. LATOUR, F PARIS, FRANCE, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION NEW YORK.

MULTIPLEX 'rnLtnrnolvr.

Specification of Letters Patent.

Patented Feb. 23, 1909.

Application filed May 27,1905, Serial No. 262,548.

- have invented certain new and useful Im- E provements in Multiplex Telephony, oi which the following is a specification.

This invention relates to systems for transinitting intelligence in which two or more messages are simultaneously transmitted over a single line conductor.

Although my improved system is readily l applicable to the transmission of signals of any sort, I contem late using it principally for multiplex telep ony with the object in View of permitting two or more ersons to freely converse over the same wire at the same time.

In carrying out my invention I impress on the line wire an alternating current and I provide suitable means for superimposing on the positive half waves of this current a series of fluctuationssuc-h as are given out by an ordinary telephone transmitter when that instrument is sub'ected to sound vibrations produced by the human voice. Similarly I superimpose on the negative hall wave fluctuations produced in a second transmitter. As all of one message is carried by the positive half waves of the alternating current and all of the other message is carried by the neg- 1 ative half waves, certain special means are necessary at the sending station for impressing on each of these half waves the proper fluctuations and for subsequently delivering these two kinds of half waves to the line conductor as an alternating current. Similarly there must be provided at the receiving station means for sorting out the positive half waves from the negative half waves, and thus delivering to the receiving instruments their respective messages. To effect this selective action on the alternating current I may make use of the eculiar property of a mercury va or recti er whereby half waves of one I po arity are freely transmitted while half waves of the other polarity are entirely-suppressed.

The details of my invention will be better understood by reference to the drawing forming a part of this specification, and the novel features are set forth with particularity in the appended claims.

Figure 1. shows an arrangement of mercury rectifiers and telephone instruments whereby two messages may be simultaneously trans- Initted in either direction over the same line wire; Fig. 2 is a diagram showing various Wave forms of the alternating current together with the fluctuations superimposed thereon by a telephone transmitter; Fig. 3 is a modification in which the long distance transmission is made with high potential alternating current; Fig. 4 shows a special means of compensating for the fluctuations produced in the receiving circuit by the alternating current so that these pulsations produceno appreciable sound in the receiver; Fig. 5 is a diagram showing the neutralizing action of the current carried by the compensator wire; Fig. 6 shows an arrangement whereby my improved system may be applied to telephone systems of a type in commen use; Fig. 7 is a diagram showing the advantage obtained by using an alternator or other current source having a rectangular current wave. Fig. 8 shows the compensator energized by a separate source, and Fig. 9 illustrates the use of a local circuit for magnetizing the core of the receiver.

In several of the figures of the drawing I have shown mercury rectifiers, and as these are all of the same type and operate in the same way it will suffice to describe in detail only one.

Referring to Fig. 1, the rectifier 1 comprises an evacuated tube 2 of glass, or other suitable material having sealed therein two carbon electrodes 3 and 4, and also carrying a mercury electrode 5. A condensing chamber 7 is located near the cathode 5. A storage battery 6 or other source of direct current is connected between the electrodes 4 and 5,, and when current has once been established between these electrodes by shaking or tilting the tube to form an are, this storage battery 6 causes a continuous flow of current through the tube from electrode 4 as anode to electrode 5 as cathode. It has been found that such a flow of current will make a mercury vapor tube conductive for current flowing toward the excited cathode, while the tube will remain nonconductive for current tending to flow from the cathode. Thus if an alternating pressure is impressed on electrodes 3 and 5 current will fiow'for the half waves during which time I electrode 5 is cathode, but will not flow during the other half period. In this manner each of the mercury rectifiers shown in the several figures of the drawing operates ass.

valve to ermit the passage of current of one I polarity, ut entirely cuts off the flow of the other polarity. I iindit desirable to provide a sma pl above the surfaceof the mercury as I am thereby enabled to operate the rectifier on} smaller currents and'with lessliability ofdisturbing fluctuations in the arc.

. In Fig.1 th line conductor mercury rectifiers 1 and 19 are interposed I between. the alternator 9 and the line wire 8 and so'connected that the half waves of current flowing to the line will pass through rectifier 1, while the half waves of current flowing from the line will pass through rectifier 10. These half waves of current pass" respectively through the transmitters 11 and 12 and the receivers 13 and 14. At the re- .20v

ceiving station the rectifiers 15 andl Gare also arranged in opposition so that current from theline wire 8 will pass by way of rectifier 15, whereas current tothe line wire Swill pass through rectifier 16'. These rectifiers are provided respectively with transmitting instru- 'ments 17 and 18 and receiving instruments 19 and 20. 1 With the arran v e'ment of circuits above described itis possi le bytalking in a sending transmitter, as for instance transmitter 11,.-

to superiinpose on-the alternating half wave passing through rectifier 1, a series of pulsations corresponding to the fluctuations in sound producedby the voice of the operator. This relation is shown in Fig. 2 in which 21' is the normal half wave ofcurrent sufpplied by the alternator, and 22 shows'the ct of the superimposed fluctuations. This half wave of current 21 passes through the line wire 8 and through rectifier 15 to the receiver 19 where the'fluctuations originally duced as sound vibrations.

produced by' thetransmitter 11 are re ro- After the wave of current 21 has passed through the transmitter. 11 there follows an interval of time corresponding to 180 electricaldegrees during which no current flows through the transmitter, and consequently during which :may be called the persistency of the human earbridges over the spaces the transmitter. 7

During the transmission of the message as not filled in'by above described a second message may be transmitted from the transmitter 12 to the atinum Wire 5 projectingv '8 is supplied by current from analternator 9,-and two receiver 20, orlfrom the transmitter 18 to the receiver 1 L As this second message 1s v transmitted. b the missing or negative half waves it may tionon the line wire 8 without interfering in e transmitted in either direcany way with the message first mentioned.

Although I have shown aground connec- .tion for the alternator and the distant end of the telephone system, it is obvious that a metallic return may beused', if such an arrangement' appears desirable. It is also obvious that instead of the'alternator 9, delivering asme curve as-shown at 21 in Fig. 2, I mayuse an alternator delivering a rectangular half Wave 23 on which the fluctuations of the transmitter maybe superimposed,' as shown at-24, or I may use a rotating switch driven in any suitable manner and servlng to impress on the system the pressureof a storage attery or-other source of direct current.

It has been noted that under certain-'conditions of excitation a mercury rectifier oifers an appreciable counter E. M.- F., and if the alternator gives a sine curve, there may 1.

ela se a small interval of time during each this counter E. M. F. of the arc. To obviate this diificulty I may, if'desired, insert storage batteries-25 and 26in series with the mere cury arcs and having an electromotive-force approximately equal to the counter E.- M. F. o

the arc.v These batteries are connected in' series with the arcs in such a way that theyassist the flow of current through the are, or

in other words just counter-balance the; f

counter E. M. F.v and therefore flow of current when the potentia difierence between the electrodes is very small.

Fig. shows'an arrangement in n 1any.re-' spects similar to thatdescribed in Fig. 1 ex-' cept that the long distance transmission is ermit the made with current at a higher potential than that used to operate the instruments. The rectifiers 27, 28, 29 and 30 are in all respects similarto those described in connection with Fig. 1, but the pulsating current delivered by rectifier 27, instead of passing through the line wireto the distant receiver passes throu h the primary 31 of a transformer and then ack to the alternator 32. Similarly thecurr'ent transmitted by reetifier28 comes 7 from the alternator 32 through the t'r'a'nsformer winding 31, and as a result an alternating pressure is generated in the winding 33 and transmitted through the line wires to the distant transformer winding 34 athigh pressure. formed down and delivered from the low pressure winding 35to the rectifiers 29 and 30. By the use of high otential currents in the line wires I reduce t e resistance loss in the wires, and am able to T transmit over longer distances than are practicable with low potentlal currents. In addition to the At the distant station it is trans 90 wave before the I alternating pressurebuilds up to a value suflicient to over-power fluctuations which produce speech there is also noticeable in the receiving instrumentsa humming sound due to the pulsations of the main alternating current. To overcome the disturbing influence of the alternator current I make use of a compensating current to, nontralize the large pulsations in the receiving instruments without interfering in any way with the speech fluctuations. This arrangement is shown diagrammatically in Fig. 4, though it is to be understood that I may apply this compensating effect to any of the receivers shown in the various figures of the drawing. The system shown in Fig. 4 is in many res ects similar to the system illustrated in ig. 1, except for the presence of the compensating line wire, and a transformer for rendering the current carried by the compensator available for neutralizing the current, flow in the receiving instruments. The rectifiers 36 and 37 are connected in opposition to the alternator 38, and are also connected through transmitters 39 and 40 to the line wire 41. The receiving instruments are not connected in series with branches of the line wire as shown in Fig. 1, but in lieu of that arrangement are connected to the secondaries of transformers. Receiver 42 is connected to the secondary 43 ofthe transformer on the core of which are also located two primaries 44 and 45. Primary 44 receives current from the line wire 41, whereas primary 45 receives current from the compensator wire. The magnetic effects of these currents are in direct op osition with the result that they complete y neutralize, leaving coil 43 uninfluenced by the pulsations of the alternator 38. Fig. 5 shows, in curve 46, the magnetic fluctuations established by the current passing through the primary 44 when the system is not being used for the transmission of speech, and in curve 47 the magnetic variations established by current transmitted through the compensator. Curve 48 shows the magnetic variations established by speaking in the transmitter 39; while curve 49 shows the resultant magnetic fluctuations available for establishing a varying otential in coil 43. It is obvious that t 1e current supplied through the compensating line wire must be in synchronism with that transmitted by the main line and must be of pro er magnitude to just blot out the effect of t e alternating half wave transmitted through the line. To secure the proper division of current through the line wire, and through the compensator,

I introduce a resistance 50 in the compensator.

\ Fig. 6 shows the manner in-which I contemplate applying my invention to telephone s stems of the typenow in common use.

he four transmitters 51, 52, 53 and 54 are,

each supplied by current from a storage battery and are each connected through the primary of a transformer. An alternator 55 sends current through the rectifiers 56, 57, 58 and 59 in the directions shown by the arrows. If when a lalf wave of current is passing through transformer coil 60 toward the rectiiier 56, the operator talks in the transmitter 51, fluctuations will be im ressed on this half wave of current which uctuations will be reproduced in the receiver 61. at the other end of the line. This half wave passes through the rectifiers 56 and 59, and does not in any way ail'ect the circuit through rectiliers 57 and 58, so that a second message may be simultaneously transmitted through this path. From an inspection of the direction of the current flow through rectifiers 56 and 57 it will be seen that there is a comparatively low resistance path from transformer coil 60 through rectifiers .56 and 57 and back to coil 60, and it might be supposed that the fluctuations produced in' this coil would take this shorter path at the sending station, and would not ass out over the line conductors as above escribed. I find, however, that such is not the case, at least when the fluctuations are produced byvibrations of the voice, although I have found that if the sound is a prolonged sound, such for instance as may be produced by whistling, there is under certain conditions a flow of current in this local path so that vibrations impressed on the transmitter 51 may be heard in the receiver 62. To overcome possible interference of the two messages in this way I introduce two batteries 63 and 64 in this local circuit so connected that their voltage is in the same direction as the counter E. M. F. of the arcs. in the rectifiers 56 and 57, or in other words in such a direction as to oppose the flow of current through a local circuit including both rectifiers.

-When the arrangement just described is used, I find it is possible to substitute for the alternator 55 a rotating commutator driven in any suitable manner and serving to impress on the line conductor current waves of a rectangular form. The reason for this will be better understood by reference to Fig. 7 in whiclrthe line 65 may be considered to represent the base line of the alternating current wave and in which the height of dotted line 66 above this base line may represent the pressure of battery 63. It will be noticed that when a pressure wave 67 is impressed on x such a system there is a certain interval of time represented by the s ace 68 during which no current flows throng the circuit, and consequently during which the fluctuations roduced by the voice vibratibns are lost. if on the other hand the wave form of pressure is rectangular. as shown in curve 69, the pressure jumps immediately to its maximum value and all the flUCllllSttlOIlSdUG to voice vibrations are preserved.

The system just described has the important advantagethat it maybe built up out of a tele hone system of ordinary form bythe simp e-addition' of mercury rectiflers and other minor details.

Fig. 8 illustrates a system inwhich th ecompensator 70'operates from a separate source consisting of an alternator 71 and, a

lamp or valve 73.. The alternator71operiates in synchronism with the main alternator 72. "lhe lamps 74, 75, 76 and 77-have ample capacity for supnlyingall the-lines 78, 79 and I 80, and the'sin e-compensator 70 serves'to control the magnetization ofall the receivers.

81, 82, 83, 84, 85 and 86'. In the drawing the telephone receivers 81 to 86 are illustrated diagrammatically as having an auxiliary -WiJIdin connected to the compensator circuit. uch arrangement will be readily un- 1 derstood-by a erson skilled in the .art and mightpro erly erepresented diagrammatic-- ally as in ig."9, wherein87 is the telephone 'core,f88 the diaphragm,- 89 the winding receiving'linecurrent, and 90 the windingconnected to the compensator circuit. This construction difiers somewhat from the construction shown in Fig. 4, and the latter was used more for purposes of clearly illustrating the arrangement than as a commercialform pensator circuits 90 and 91- are in a local cirof device. a In the system shown in Fig. 9, the comcuit supplied with energy through a lamp 92. It Wlll be understood that the alternator 93 ma be maintained in proper synchronismr wit the system in a manner well known to electricians. r I 1 :Vihat I claim as new, and

1. In a systemofelectrical .communica- .t1on, a lme conductoni-meansfor' impressing on sand conductor a current whlch per1od1c- .ally reverses in sign, means for impressingon the-current waves of one sign fluctuations 2. In a system of electric signaling, a line conductor, means for mpresslng' on said conductor a current which periodlcally reverseswaves of one sign fluctuations corresponding corresponding in. frequency and-magnitude to the signals or messagesto be communicated and means for diverting current waves of the opposlte sign through a shunt path.

in sign,.mea ns for im'pressing'on the current in frequency and magnitude to the signals to hetr'ansmitted, and means forindependently impressing on the waves of the ot ductor, means 'for impressing on said, line conductoncurrent p 'ls'ationsof one polarity which succeed ea'c other at regular inter- .vals, means for superimposing. on said current pulsations, fluctuations corresponding in frequency and magnitude to voicevibrav desire't'o secureby Letters Patent of the United States, is,

er'polar-f -1ty. 'a second series of fluctuations for the transmission of a second signal. Y

' I 3. Int. system of telephony, a line eon-' tion s, means forut-ilizing said fluctuations, to

produce sound and independent means fortransmitting current waves of. opposite polarity to said line conductor.

4.- In a system of multiplex telephony, a line wire/a transmitter connected thereto, means for passing an alternating. current through said line wire, and an asymmetrical I conductor for preventing the flow of current in one direction to said telephone transmitter but permitting the flow of the current in the. opposite direction therethroughll I '5. In a system of multiplex telephony, line conductor, atelephone receiver connect: e'd thereto, means for impressing an alter-.

nating current'on said line conductor,'and an asymmetrical conductor preventin the flow "of currentin one direction'throug "said're ceiver but permitting the how of current -in the opposite'direction there'through.

6; n a'system of electric signaling, a line conductor, a source of alternating current connected thereto through ;a plurality of paths, asymmetric conductors for causing the current of one polarity to ass through one .ofsaid paths and current '0 the o I fposits polarity to pass. throu h another 0 said paths, means associate with each of said paths for superimposing on the current passmg therethrough fluctuations corres ending,

to the signals to be transmitted, an means for utilizing to the influence of un directional current'pulintervals and which have superimposed thereon fluctuations of a higherfrequene I than said pulsations, and means for neutra izing the effect of said pulsations on saidreceiveiai I 8. In a system of tele hony, a 'line con-- of-one polarity, and a transmitter for superimposing on said pulsations fluctuations corresponding in frequency" and magnitude. to

voice vibrations. I

9.- In a system of-electrical slgnallng, ava- 11' por electric devioe'for transmitting positive pulsations to said conductor, a second vapor electric devlce for transmitt ng negatrvelunpulses .to said conductor, means for impress I mg high'frequency fluctuations on said posi-" tive and negative pulsations," and means for produce sound waves.

utilizing said high frequency fluctuations to it: I

' ductor,.a vapor electric evice fortransmit-I ting to said line conductor-current pulsations ll l -. 10. a system of electric communication I a'line conductor, meansfor impressing on; said conductor a current which periodically; reverses in sign, -means for changmg the I waveform of current pulsations of one slg-n, vapor electric-means for separating pulsations of difierent sign, and means for detectsaid changes in the wave form of said pu tions.

11. In a telephone system, the combination of a line conductor, a source of alternating current, vapor rectifiers connected therewith for separating pulsations of, unlike polarity, a transmitter for current of each polarity for superimposing fluctuations thereon, means'for recombining the currents of unlike polarity for transmission through said line conductor, means for again separating currents of unlike polarity, and receiving instruments operated by said separated currents.

'12. In a telephone system, the combination of a transmitter connected through a battery to a transformer winding, a second Winding for said transformer, a mercury rectifier connected therewith, means for supplying unidirectional pulsations than 11 said mercury rectifier and its associate transformer winding, line conductors in circuit therewith, and a receiving instrument actuated by energy transmitted through said line conductors.

13. In a system of multiplex telephony, a line wire, a transmitting means connected thereto, means for transmitting an alternating current through said line wire, and a mercury vapor device for transmitting current of one polarity to said transmitting means but 0 posing .a prohibitive resistance to current 0 op osite polarity.

In witness w ereof, I have hereunto set my hand this twelfth day of Ma 1905.

MARIUS C. A. ATOUR.

Witnesses:

HANSON 0. (30x12, JOHN BAKER. 

